This section provides background information related to the present disclosure which is not necessarily prior art.
The Economy (ECO) mode of an Un-interrupted Power Supply (UPS) system is a power saving mode which is suitable for the current low-carbon, green, and energy-saving concepts. In ECO mode, when the bypass module operates to supply power to the load, the UPS supplies power to the load via a bypass module in the UPS, while an inverter of the UPS stands by. In the conventional ECO mode, the inverter is in a stand-by mode for a long time, since the UPS switches to an inverter supplying mode only when the bypass is turned off or operates abnormally. In such a case, if the load of the UPS is a non-linear load, the bypass module may generate harmonics when supplying power, which may pollute the grid and even cause a local grid abnormality.